The objectives are: 1) to determine how phonatory efficiency is altered in various types of laryngeal pathology, and 2) whether changes in laryngeal structure and neural control alter phonatory efficiency. A preliminary study was completed of the alterations in phonatory efficiency in two patients in comparison with normal; one with vocal fold nodules, the other with unilateral paralysis. The results indicated that efficiency was impaired in the patient with vocal fold nodules while it exceeded normal levels in the patient with unilateral paralysis. The validity of the concept of an optimum phonatory efficiency at a particular fundamental frequency, was assessed in the normal controls and each of the patients. Efficiency increased as fundamental frequency increased in the normal speakers while no systematic relationship with fundamental frequency was found in the patients. Methods of studying phonatory efficiency have been improved and instrumentation developed for measuring physiological aspects of phonatory function. Studies of phonatory efficiency are continuing in additional numbers of patients with the improved experimental and measurement techniques. Patients sustaining unilateral damage to the recurrent laryngeal nerve during thyroidectomy for carcinoma are being followed to determine whether phonatory efficiency changes with the return of nerve function. Also, when there is no change in nerve function, phonatory efficiency will be monitored to examine whether there are compensatory changes in the mode of phonation which alter phonatory efficiency.